diff options
Diffstat (limited to 'contrib/gcclibs/libgomp/libgomp.texi')
| -rw-r--r-- | contrib/gcclibs/libgomp/libgomp.texi | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/contrib/gcclibs/libgomp/libgomp.texi b/contrib/gcclibs/libgomp/libgomp.texi index c48cf93e089f..f92a5da77fd8 100644 --- a/contrib/gcclibs/libgomp/libgomp.texi +++ b/contrib/gcclibs/libgomp/libgomp.texi @@ -895,14 +895,25 @@ dynamic scheduling and a chunk size of 1 is used. @cindex Environment Variable @table @asis @item @emph{Description}: -A patch for this extension has been submitted, but was not yet applied at the -time of writing. - -@item @emph{Reference}: -@uref{http://gcc.gnu.org/ml/gcc-patches/2006-05/msg00982.html, -GCC Patches Mailinglist} -@uref{http://gcc.gnu.org/ml/gcc-patches/2006-05/msg01133.html, -GCC Patches Mailinglist} +Binds threads to specific CPUs. The variable should contain a space- or +comma-separated list of CPUs. This list may contain different kind of +entries: either single CPU numbers in any order, a range of CPUs (M-N) +or a range with some stride (M-N:S). CPU numbers are zero based. For example, +@code{GOMP_CPU_AFFINITY="0 3 1-2 4-15:2"} will bind the initial thread +to CPU 0, the second to CPU 3, the third to CPU 1, the fourth to +CPU 2, the fifth to CPU 4, the sixth through tenth to CPUs 6, 8, 10, 12, +and 14 respectively and then start assigning back from the beginning of +the list. @code{GOMP_CPU_AFFINITY=0} binds all threads to CPU 0. + +There is no GNU OpenMP library routine to determine whether a CPU affinity +specification is in effect. As a workaround, language-specific library +functions, e.g., @code{getenv} in C or @code{GET_ENVIRONMENT_VARIABLE} in +Fortran, may be used to query the setting of the @code{GOMP_CPU_AFFINITY} +environment variable. A defined CPU affinity on startup cannot be changed +or disabled during the runtime of the application. + +If this environment variable is omitted, the host system will handle the +assignment of threads to CPUs. @end table |